One of my favorite childhood treats were pink and white circus animal cookies; and honestly, I still love them! In a quest to create a copycat version of my fave cookies, I have come up with what I think is the best rendition out there.
Place butter in the bowl of an electric stand mixer or use a medium bowl and electric hand-mixer. Beat butter for 30-60 seconds until creamy. Add the powdered sugar and beat again just until creamy and well-combined. Add the egg and vanilla. Beat again just until combined. Add the flour, baking soda, and salt all at once and beat on low speed just until dough starts to come together, 1-2 minutes. It's okay if there is some unincorporated flour. Stop the mixer and scrape down the sides of the bowl and finish mixing dough with a wooden spoon or silicone spatula.
Turn dough out onto a large square of plastic wrap or waxed paper and use the sides of the wrap or paper to pull the dough together into a ball. Flatten into a disk that is about 1-inch in thickness. Wrap well and chill for at least 30 minutes.
When ready to bake cookies, remove dough from fridge and let stand for a few minutes at room temperature to make it easier to roll. Preheat oven to 350°F and line two baking sheets with parchment paper.
Using two pieces of parchment paper or a lightly floured surface, roll the dough into a large rectangle or oval that is about 1/4-inch thick. Using the small cookie cutters, cut the dough into animal shapes and transfer to the prepared baking sheets.
Bake at 350 for about 10 minutes °F.
To decorate: Line two baking sheets with wax or parchment paper. Melt white candy melts according to package directions. Dip half of the cookies into the white candy melts, allowing the excess to drip back into the bowl. Place on the waxed or parchment paper. Immediately after dipping, sprinkle with a pinch of the rainbow nonpareils. Repeat with pink candy melts and remaining cookies. Allow cookies to harden completely before removing from the paper. Store in an airtight container for several weeks in a cool, dry container. (Cookies can be refrigerated or frozen, if needed, but are fairly shelf stable.)